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The name "octopus" means literally "eight feet" and this animal does indeed have eight arms, joined at their bases by a web and surrounding a beaked mouth. Although some specimens may reach a span of 10 feet, the average is approximately 3 feet.
Distribution and Habitat
This octopus has a world-wide distribution, being found in all oceans (except the Arctic), as well as the Mediterranean and Caribbean seas. It lives in tropical, subtropical, and temperate waters between the surface and a depth of 300 to 500 feet.
The arms are very sensitive to touch and taste, and the eyes are well developed. The importance of vision is reflected in the octopus's outstanding ability to change color. This is done with two kinds of chromatophores (pigment cells) in the skin that vary in color according to how much they are expanded or contracted. One kind varies from black to red-brown and the other from red to pale orange-yellow. Beneath these chromatophores is a layer of small bodies known as iridocytes that reflect white light or give a blue or green by refraction. The variation in appearance is also a matter of posture and of general texture. The arms may be extended, tucked underneath, or curled stiffly back over the body as armor and the suckers may be out of sight or protruded to give the arms a wavy outline. By suitable adjustments in color, posture and texture an octopus can merge completely with its background, and it can do so very quickly. What's more, the octopus's "quick change" is done intentionally, with a specific result intended. That is, rather than simply take on the color, texture, etc. of its background, an octopus may also use its camouflage ability to "create" a lure to attract prey. It can also, if necessary, take on the coloring and/or posture of a poisonous animal in order to deter potential predators. Observations have also shown that an octopus will take on various colors, textures, etc. to express moods, and some have been seen changing colors, etc. for no apparent reason at all.
Can you spot the octopus amongst the coral?
A bottom-dwelling animal, the octopus makes its home in a hole or rock crevice in shallow water. By day, it spends most of its time hidden in its lair. When outside, it creeps about on its arms most of the time, using its suckers to grip, though it can also swim. It usually swims headfirst with its arms trailing, by blowing water out through its siphon. It is a solitary and territorial animal, with individuals coming together only for breeding purposes.
The octopus swims headfirst.
The octopus does most of its hunting at night, emerging from its lair to seek crabs, crayfish, and other molluscs. It catches most of its prey by stealth. Using its camouflage abilities to blend in with its surroundings, it waits for prey to pass by and then seizes it with its long arms. The arms are powerful and flexible, with two rows of suckers that help it grip its prey. Once caught the prey is stunned with a secretion of nerve poison. To stalk lobsters and other potentially dangerous prey, the octopus squirts ink into the water to form a screen, from behind which it creeps up on its victim.
Close-up look at the octopus's suckers.
The octopus is preyed upon by moray and conger eels, dolphins, and sharks. Whenever possible, the octopus will escape from its predators by shooting a jet of water through its body to create a burst of speed.
The octopus's ink sac also helps it avoid predators. It releases a disorienting black cloud that is accompanied by another secretion to dull the attacker's sense of smell.
Releasing a cloud of ink in order to escape
Prior to mating, the male approaches the female, who fends him off for a while, but then submits to him. During mating, the male sends waves of spermatophores down one of his arms -- the hectocotylus -- into the female's mantle cavity to fertilize her eggs. Copulation may last for several hours, and the same pair may mate several times over a period of week or so.
An octopus egg reveals the embryo within.
Eggs are laid in shallow water. On rocky shores, females find a hole, crevice or sheltered place and often protect their nests with shells, stones and other solid objects that they gather. On sandy or muddy bottom, eggs are laid in empty mollusc shells or in man-made objects such as cans, bottles, tires, boots, etc. The total number of eggs laid varies from 100,000 to 500,000, and it may take up to a week or more for all eggs to be laid.
The female will not leave her nest in the four to six weeks that it takes for her eggs to hatch. Because they rarely eat at all while guarding their eggs, it is not uncommon for females to die of starvation. Even in captivity it is almost impossible to coak a mother octopus away from her eggs. She may refuse to eat even if food is dropped right next to her.
A female octopus zealously guarding her eggs.
Egg care includes cleaning the eggs with the arms tips and directing jets of water from the funnel through the strings. The eggs hatch into 1/4-inch larvae that look like tiny versions of their parents. They come to rest on the seabed, where they mature quickly. Larvae prey on plankton until reaching maturity, at about 45 to 60 days of age.
Octopuses live for about 12 to 18 months in the wild.
The octopus has incredible vision for a marine animal. The well-developed eyes have a large cornea which gives them a range of vision of 180 degrees.
The octopus's eyes give it a range
of vision of 180 degrees.
The octopus is capable of learning. In an experiment, octopuses were trained to distinguish between shapes and to recognize objects by touch. Other studies have proven that octopi are capable of solving problems, with the most well known experiment showing an octopus opening a jar in order to get the food inside.
The first writing ink was made from pigment found in the octopus's ink sac.
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This page was last updated on July 11, 2018.